Epinine and related compounds of the formula ##STR1## wherein R is a hydrogen atom or a hydrocarbyl group such as alkyl, aryl, cycloalkyl, aralkyl, alkenyl, cycloalkenyl, etc., can be oxidatively cyclized to bicyclic quinones, which in turn can be isomerized to the 5,6-dihydroxindoles, a group of compounds useful as dyes and/or dye intermediates, and as antioxidants and oxygen getters for organic systems. For example, epinochrome, a deep-red water-soluble compound, can be formed by the oxidative cyclization of epinine (Formula I above; R=methyl) and then isomerized to 5,6-dihydroxyindole--see Wyler et al, Helv. Chem. Acta 1968, 51, 1476. Improved processes for effecting the conversion of compounds of Formula I to 1H-indole-5,6-diones, 5,6-dihydroxyindoles, and 5,6-diacyloxyindoles, are described in my co-pending applications Ser. Nos. 396,345 and 396,139, filed contemporaneously herewith, both now abandoned. In addition to these utilities, compounds of Formula I have application as adrenergics, and particularly as vasoconstrictors.
Unfortunately the compounds of Formula I above are quite expensive and difficult to prepare. See the procedures described by Pyman, J. Chem. Soc. 1909, 95, 166; Buck, J. Am. Chem. Soc. 1930, 4119; and Bretschneider, Monatsh. 1947, 76, 335, which involve inefficient chemistry with functional group protections and deprotections.
A welcome contribution to the art would be the provision of a new and highly efficient method for the synthesis of compounds of Formula I above.